dmaengine: fix use-after-free in dma_chan_put() and dma_release_channel()grafted

When dma_device_put() drops the last reference on chan->device->ref,
dma_device_release() runs and may free the dma_device along with its
channels.

dma_chan_put() then still reads chan->device->owner via
dma_chan_to_owner() for the trailing module_put(). KASAN catches it:

	slab-use-after-free in dma_chan_put+0x3e6/0x4c0
	Read of size 8 by task insmod/6319
	Freed by task 6319:
	  kfree+0x225/0x470
	  dma_chan_put+0x395/0x4c0
	  dmaengine_put+0xf8/0x160

Cache the module owner in dma_chan_put() before the put so the trailing
module_put() does not need chan->device.

Fixes: 8ad342a86359 ("dmaengine: Add reference counting to dma_device struct")
Suggested-by: Sashiko <sashiko-bot@kernel.org>
Link: https://sashiko.dev/#/patchset/20260518-dmaengine-kref-fix-v1-1-4d6125048fb7@amd.com
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: Shivank Garg <shivankg@amd.com>
Link: https://patch.msgid.link/20260822-dmaengine-kref-fix-v5-3-d4a4ee47d927@amd.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

1 files changed, 95 insertions, 0 deletions

diff --git a/include/net/compat.h b/include/net/compat.h
new file mode 100644
index 000000000..84c163f40
--- /dev/null
+++ b/include/net/compat.h
@@ -0,0 +1,95 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef NET_COMPAT_H
+#define NET_COMPAT_H
+
+
+struct sock;
+
+#include <linux/compat.h>
+
+struct compat_msghdr {
+	compat_uptr_t	msg_name;	/* void * */
+	compat_int_t	msg_namelen;
+	compat_uptr_t	msg_iov;	/* struct compat_iovec * */
+	compat_size_t	msg_iovlen;
+	compat_uptr_t	msg_control;	/* void * */
+	compat_size_t	msg_controllen;
+	compat_uint_t	msg_flags;
+};
+
+struct compat_mmsghdr {
+	struct compat_msghdr msg_hdr;
+	compat_uint_t        msg_len;
+};
+
+struct compat_cmsghdr {
+	compat_size_t	cmsg_len;
+	compat_int_t	cmsg_level;
+	compat_int_t	cmsg_type;
+};
+
+struct compat_rtentry {
+	u32		rt_pad1;
+	struct sockaddr rt_dst;         /* target address               */
+	struct sockaddr rt_gateway;     /* gateway addr (RTF_GATEWAY)   */
+	struct sockaddr rt_genmask;     /* target network mask (IP)     */
+	unsigned short	rt_flags;
+	short		rt_pad2;
+	u32		rt_pad3;
+	unsigned char	rt_tos;
+	unsigned char	rt_class;
+	short		rt_pad4;
+	short		rt_metric;      /* +1 for binary compatibility! */
+	compat_uptr_t	rt_dev;         /* forcing the device at add    */
+	u32		rt_mtu;         /* per route MTU/Window         */
+	u32		rt_window;      /* Window clamping              */
+	unsigned short  rt_irtt;        /* Initial RTT                  */
+};
+
+int __get_compat_msghdr(struct msghdr *kmsg, struct compat_msghdr *msg,
+			struct sockaddr __user **save_addr);
+int get_compat_msghdr(struct msghdr *, struct compat_msghdr __user *,
+		      struct sockaddr __user **, struct iovec **);
+int put_cmsg_compat(struct msghdr*, int, int, int, void *);
+
+int cmsghdr_from_user_compat_to_kern(struct msghdr *, struct sock *,
+				     unsigned char *, int);
+
+struct compat_group_req {
+	__u32				 gr_interface;
+	struct __kernel_sockaddr_storage gr_group
+		__aligned(4);
+} __packed;
+
+struct compat_group_source_req {
+	__u32				 gsr_interface;
+	struct __kernel_sockaddr_storage gsr_group
+		__aligned(4);
+	struct __kernel_sockaddr_storage gsr_source
+		__aligned(4);
+} __packed;
+
+struct compat_group_filter {
+	union {
+		struct {
+			__u32				 gf_interface_aux;
+			struct __kernel_sockaddr_storage gf_group_aux
+				__aligned(4);
+			__u32				 gf_fmode_aux;
+			__u32				 gf_numsrc_aux;
+			struct __kernel_sockaddr_storage gf_slist[1]
+				__aligned(4);
+		} __packed;
+		struct {
+			__u32				 gf_interface;
+			struct __kernel_sockaddr_storage gf_group
+				__aligned(4);
+			__u32				 gf_fmode;
+			__u32				 gf_numsrc;
+			struct __kernel_sockaddr_storage gf_slist_flex[]
+				__aligned(4);
+		} __packed;
+	};
+} __packed;
+
+#endif /* NET_COMPAT_H */